Method of exchanging messages for transmission power control between devices in a wireless network, and devices for the same

ABSTRACT

A method of exchanging messages for link recommendation in a receiving device of a wireless network comprises receiving a first data packet from a transmitting device; and transmitting link recommendation information to the transmitting device, the link recommendation information including transmit power control (TPC) information for controlling transmission power to be used for a second data packet in the transmitting device.

This application claims the benefit of the U.S. provisional PatentApplication No. 61/155,503, filed on Feb. 25, 2009, and the KoreanPatent Application No. 10-2009-0119813 filed on Dec. 4, 2009, which arehereby incorporated by reference as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless communication system, andmore particularly, to a method of controlling transmission power forlink-adaptive data transmission in a wireless communication system anduser devices for the method.

2. Discussion of the Related Art

Recently, Bluetooth and wireless personal area network (WPAN)technologies have been developed, which form a wireless network betweena relatively small number of digital devices in limited places such ashomes or small companies to allow audio or video data to be exchangedbetween the devices. The WPAN can be used for information exchangebetween a relatively small number of digital devices in a relativelyclose distance, and enables low power and low-cost communication betweenthe digital devices. IEEE 802.15.3 (Wireless Medium Access Control (MAC)and Physical Layer (PHY) Specifications for High Rate Wireless PersonalArea Networks (WPANs)) approved on Jun. 12, 2003 defines specificationof a MAC layer and a physical (PHY) layer of high rate WPAN.

FIG. 1 is a brief diagram illustrating an example of a wireless privateaccess network (WPAN).

As illustrated in FIG. 1, the WVAN is a network configured betweenpersonal devices within a limited space such as home, and allowsinformation to be exchanged between applications without seamlessness byconfiguring a network through direct communication between devices.Referring to FIG. 1, the WPAN includes two or more user devices 11 to15, one of which acts as a coordinator 11. The coordinator 11 providesbasic timing of the WPAN and serves to control quality of service (QoS)requirements. Examples of the user devices include computers, PDAs,notebook computers, digital TVs, camcorders, digital cameras, printers,mikes, speakers, headsets, bar-code readers, displays, and cellularphones. All digital devices can be used as the user devices.

The WPAN is not predesigned but is an ad hoc network (hereinafter,referred to as ‘piconet’) formed if necessary without assistance of acentral infrastructure. A procedure of forming one piconet will bedescribed in detail. The piconet starts as a random device that can beoperated as a coordinator performs the function of the coordinator. Alldevices perform scanning before associating with the existing piconet orstarting a new piconet. Scanning means that a device collects and storesinformation of channels and searches whether the existing piconetexists. A device that has been commanded from an upper layer to start apiconet forms a new piconet without associating with a piconetpreviously formed on a random channel. The device starts a piconet byselecting a channel having little interference based on data acquiredduring scanning and broadcasting a beacon through the selected channel.In this case, the beacon means timing allocation information,information of other devices within a piconet, and control informationbroadcasted by the coordinator to control and manage the piconet.

FIG. 2 is a diagram illustrating an example of a superframe used in apiconet. Timing control in the piconet is basically performed based onsuperframes. Referring to FIG. 2, each superframe starts by means of thebeacon transmitted from the coordinator. A contention access period(CAP) is used to allow devices to transmit commands or asynchronous databased on contention. A channel time allocation period includes amanagement channel time block (MCTB) and a channel time block (CTB). TheMCTB is a period where control information can be transmitted between acoordinator and a device or between devices. The CTB is a period whereasynchronous data or isochronous data can be transmitted between adevice and a coordinator or between other devices. For each superframe,the number, length and location of CAPs, MCTBs, and CTBs are determinedby the coordinator and transmitted to other devices within the piconetthrough the beacon.

When a random device within the piconet needs to transmit data to thecoordinator or other device, the device requests the coordinator toallocate channel resources for data transmission, and the coordinatorallocates the channel resources to the device within the range ofavailable channel resources. If the CAP exists within the superframe andthe coordinator accepts data transmission in the CAP, the device cantransmit data of small capacity through the CAP without being allocatedwith channel time from the coordinator.

If the number of devices within the piconet is small, since channelresources for data transmission from each device are sufficient, noproblem occurs in allocation of channel resources. However, if channelresources are insufficient due to a large number of devices, or if dataof large capacity such as moving pictures are transmitted, a problem mayoccur in that channel resources are not allocated to the other deviceseven though the other devices have data to be transmitted, wherebycommunication cannot be performed.

Also, during data communication between two or more devices that belongto the WVAN, communication quality may be deteriorated depending on thestatuses of the devices, such as an obstacle occurring between thedevices and interfering with communication, change of the distance orlocation between the devices, and interference caused by anotherneighboring device.

In this respect, various methods for efficiently performing datacommunication between devices constituting WVAN without any problem arebeing studied.

SUMMARY OF THE INVENTION

Examples of a method for link adaptation between devices of a wirelessnetwork include an unequal error protection (UEP) method, a beamsearching method, an HRP mode and/or LRP mode adjustment method, and atransmission power control method. At least one of the aforementionedlink adaptation methods can be used depending on a status of the device.Particularly, if strength of a received signal is varied, the device canperform link adaptation through the transmission power control method.

According to the general transmission power control method, a receivingdevice transmits a transmission power control request message of a MACcommand type to a transmitting device, and the transmitting devicecontrols the transmission power in response to the request message. Atthis time, in order to transmit the request message, the receivingdevice should receive channel resources for transmission of the messagefrom a coordinator belonging to the wireless network. Since thereceiving device which has not received channel resources for datatransmission from the coordinator should transmit a channel resourceallocation request message to the coordinator for transmission powercontrol and receive separate channel resources, a problem occurs in thatit is difficult to immediately control the transmission power. Also, aproblem occurs in that the receiving device can perform a transmissionpower control request only after receiving channel resources of givencapacity from the coordinator.

Accordingly, the present invention is directed to a method of exchangingmessages for transmission power control between devices in a wirelessnetwork and devices for the same, which substantially obviate ones ormore problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a method of exchangingmessages, in which a receiving device can request a transmitting deviceof immediate transmission power control in accordance with receivedsignal strength without interference with a coordinator.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, amethod f exchanging messages for link recommendation at a receivingdevice in a wireless network comprises receiving a first data packetfrom a transmitting device; and transmitting link recommendationinformation to the transmitting device, wherein the link recommendationinformation comprises transmit power control(TPC) information forcontrolling transmission power to be used for transmission of a seconddata packet in the transmitting device.

The method according to the present invention further comprisesreceiving link recommendation request information from the transmittingdevice, wherein the link recommendation request information is torequest link recommendation.

The link recommendation request information is included in a MACextension header of a second data packet received from the transmittingdevice.

The link recommendation information is included in an ACK packettransmitted in response to the second data packet. Preferably, the linkrecommendation information is included in a MAC extension header of theACK packet.

The MAC extension header comprises a extension control field comprisingcontrol information, a type field indicating a type of data included insub-packets constituting a MAC packet, an low-rate physical (LRP)antenna direction tracking (ADT) feedback field comprising ADT feedbackinformation for obtaining an optimized transmission pattern duringfuture signal transmission in an LRP unidirectional mode, an ACK groupfield comprising information indicating whether preceding sub-packetsexist and at least one of a clock field comprising clock countinformation of video data or audio data.

The extension control field comprises a link mode field indicating atype of link recommendation, a high-rate physical (HRP) mode fieldindicating a recommended HRP mode to be used at the transmitting device,a LRP mode field indicating a recommended LRP mode to be used at thetransmitting device and a TPC field comprising the TPC information.

The link mode field indicates any one of “link recommendation is notbeing requested”, “link recommendation request” and “link recommendationresponse”.

In according to the present invention, the link recommendationinformation is transmitted to the transmitting device without a requestfor the link recommendation information from the transmitting device.And, the link recommendation information is included in an ACK packettransmitted in response to a second data packet received from thetransmitting device.

The link recommendation information is determined based depending on athe result of channel status assessment for a channel on which the firstdata packet is received.

In according to the present invention, the TPC information comprises avalue indicating a recommendation for controlling transmission power inthe transmitting device.

The value indicating the recommendation indicates that no change of atransmission power is recommended. On the other hand, the valueindicates that increase of a transmission power is recommended by apredetermined amount. On the other hand, the value indicates thatdecrease of a transmission power is recommended by a predeterminedamount.

In according to the present invention, the transmit power control (TPC)information is determined depending on a receiving strength.

In another aspect of the present invention, a receiving device in awireless network comprises a transmitting module, a receiving modulereceiving a first data packet from a transmitting device; and a controlmodule generating link recommendation information and controlling thetransmitting module to transmit the link recommendation information tothe transmitting device, wherein the link recommendation informationcomprises transmit power control (TPC) information for controllingtransmission power to be used for transmission in the transmittingdevice.

In still another aspect of the present invention, a method of exchangingmessages at a transmitting device in a wireless network comprisestransmitting a first data packet to a receiving device and receivinglink recommendation information from the receiving device, wherein thelink recommendation information comprises transmit power control (TPC)information for controlling transmission power to be used fortransmission.

In further still another aspect of the present invention, a transmittingdevice in a wireless network comprises a receiving module, atransmitting module transmitting a first data packet to a receivingdevice and a control module receiving link recommendation informationincluding transmit power control (TPC) information for controllingtransmission power to be used for transmission from the receiving devicethrough the receiving module, and controlling the transmission power inaccordance with the TPC information.

The aforementioned embodiments are only a part of the preferredembodiments of the present invention, and various embodiments on whichtechnical features of the present invention are reflected can be devisedand understood by the person with ordinary skill in the art based on thedetailed description of the present invention, which will be describedlater.

According to the embodiment of the present invention, the WVAN receivingdevice can transmit a transmission power control request message forlink adaptation to the transmitting device through ACK/NACK signals evenwithout separate channel resource allocation request to the coordinator.

Accordingly, the device can perform immediate transmission power controlbased on variation of received signal strength varied depending on itsstatus. Also, the transmission power can be controlled by a linkadaptation method between devices that transmit and receive signalswithout interference of the coordinator.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is a diagram illustrating an example of a WPAN;

FIG. 2 is a diagram illustrating an example of a superframe used in apiconet;

FIG. 3 is a diagram illustrating an example of a WVAN;

FIG. 4 is a diagram illustrating a frequency band of HRP channels andLRP channels used in a WVAN;

FIG. 5 is a diagram illustrating an example of a structure of asuperframe used in a WVAN;

FIG. 6 is a diagram illustrating another example of a structure of asuperframe used in a WVAN;

FIG. 7 is a diagram illustrating a protocol layer structure implementedin a device of a WVAN;

FIG. 8 is a flow chart illustrating an example of a procedure foradaptation to a specific link in a WVAN device according to oneembodiment of the present invention;

FIG. 9 is a flow chart illustrating an example of link assessment andlink recommendation in a WVAN device according to one embodiment of thepresent invention;

FIG. 10 is a flow chart illustrating an example of a procedure oftransmitting and receiving signals to perform a beam searching processbetween WVAN devices according to one embodiment of the presentinvention;

FIG. 11A to FIG. 11E are diagrams illustrating an example that acommunication status is deteriorated by a status of a WVAN deviceaccording to one embodiment of the present invention;

FIG. 12 is a flow chart illustrating an example of a procedure ofperforming link recommendation between WVAN devices according to oneembodiment of the present invention;

FIG. 13 is a diagram illustrating another example of link recommendationin a WVAN device according to one embodiment of the present invention;

FIG. 14 is a diagram illustrating an example of a link recommendationprocedure for transmission power control for link adaptation in a WVANdevice according to one embodiment of the present invention;

FIG. 15 is a diagram illustrating another example of a linkrecommendation procedure for transmission power control for linkadaptation in a WVAN device according to one embodiment of the presentinvention;

FIG. 16 is a diagram illustrating an example of a MAC header formattransmitted from a WVAN device according to one embodiment of thepresent invention;

FIG. 17 is a diagram illustrating an example of a MAC extension headerformat transmitted from a WVAN device according to one embodiment of thepresent invention;

FIG. 18 is a diagram illustrating other example of a link recommendationprocedure for transmission power control for link adaptation in a WVANdevice according to one embodiment of the present invention;

FIG. 19 is a diagram illustrating an example of a data format thatincludes a probe request message transmitted from a WVAN transmittingdevice according to one embodiment of the present invention;

FIG. 20 is a diagram illustrating an example of a data format thatincludes a probe response message transmitted from a WVAN deviceaccording to one embodiment of the present invention; and

FIG. 21 is a diagram illustrating an example of a broadcasting signalprocessing system that includes a WVAN device according to oneembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

Hereinafter, structures, operations, and other features of the presentinvention will be understood readily by the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Embodiments described later are examples in which technicalfeatures of the present invention are applied to a wireless video areanetwork (WVAN) which is a kind of a WPAN.

FIG. 3 is a diagram illustrating an example of a WVAN. In the samemanner as illustrated in FIG. 1, a WVAN of FIG. 3 includes two or moreuser devices 22 to 25, one of which acts as a coordinator 21. Thecoordinator 21 provides basic timing of the WVAN, maintains a track ofdevices belonging to the WVAN, and serves to control quality of service(QoS) requirements. The coordinator performs its function and at thesame time serves as one device belonging to the WVAN. Other devices 22to 25 different from the coordinator 21 can start stream connection.

One of the differences between the WVAN illustrated in FIG. 3 and theWPAN of FIG. 1 is that the WVAN of FIG. 3 supports two kinds of physical(PHY) layers. Namely, the WVAN supports physical layers, high-ratephysical (HRP) layer and low-rate physical (LRP) layer. The HRP layer isa physical layer that can support a data transmission rate of 1 Gb/s orgreater, and the LRP layer is a physical layer that supports a datatransmission rate of several Mb/s. The HRP layer is highly directional,and is used for transmission of isochronous data streams, asynchronousdata, MAC command and A/V control data through unicast connection. TheLRP layer supports a directional or omni-directional mode and is usedfor transmission of beacon, asynchronous data, MAC command throughunitcast or broadcasting. The coordinator 21 can transmit or receivedata to and from other device using the HRP and/or LRP layer. The otherdevices 22 to 25 of the WVAN can also transmit or receive data using theHRP and/or LRP layer.

FIG. 4 is a diagram illustrating a frequency band of HRP channels andLRP channels used in a WVAN. The HRP layer uses four channels of abandwidth of 2.0 GHz in a band of 57 to 66 GHz, and the LRP layer usesthree channels of a bandwidth of 92 MHz. As illustrated in FIG. 4, theHRP channels and the LRP channels share a frequency band and are usedrespectively by a TDMA mode.

FIG. 5 is a diagram illustrating an example of a structure of asuperframe used in a WVAN. Referring to FIG. 5, each superframe includesa beacon region where a beacon is transmitted, a reserved regionallocated to a random device by the coordinator in accordance with arequest of the devices, and an unreserved region not allocated by thecoordinator but transmitting and receiving data between the coordinatorand device or between devices in accordance with a contention basedmode, wherein each of the regions is time divided. The beacon includestiming allocation information in a corresponding superfrmae, andmanagement and control information of the WVAN. The reserved region isused to transmit data from a device, to which channel time is allocatedby the coordinator in accordance with a channel time allocation requestof the device, to other device. Command, data streams, asynchronousdata, etc. can be transmitted through the reserved region. If a specificdevice transmits data to other device through the reserved region, theHRP channel is used. If the device that receives the data transmitsACK/NACK signal of the received data, the LRP channel is used. Theunreserved region can be used to transmit control information, MACcommand, or asynchronous data between the coordinator and the device orbetween the devices. In order to prevent data collision between thedevices in the unreserved region, a carrier sense multiple access (CSMA)mode or a slotted Aloha mode can be used. In the unreserved region, thedata can be transmitted through the LRP channel only. If there are manykinds of control information or commands to be transmitted, the reservedregion can be set in the LRP channel. In each superframe, the length andthe number of reserved regions and unreserved regions can be varied persuperframe and are controlled by the coordinator.

FIG. 6 is a diagram illustrating another example of a structure of asuperframe used in a WVAN. Referring to FIG. 6, each superframe includesa beacon field 30 where a beacon is transmitted, a reserved channel timeblock 32, and an unreserved channel time block 31. Each of the channeltime blocks (CTB) is time-divided into a HRP region to which data aretransmitted through the HRP layer and a LRP region to which data aretransmitted through the LRP layer. The beacon 30 is periodicallytransmitted by the coordinator to identify a beginning part of eachsuperframe, and includes scheduled timing information and management andcontrol information of the WVAN. The device can exchange data in thenetwork through the timing information and management/controlinformation included in the beacon.

In the HRP region, the reserved CTB field can be used to transmit datafrom a device, to which channel time is allocated by the coordinator inaccordance with a channel time allocation request of the device, toother device. If a specific device transmits data to other devicethrough the reserved CTB field, the HRP channel is used. If the devicethat receives the data transmits ACK/NACK signal of the received data,the LRP channel is used.

The unreserved CTB field can be used to transmit control information,MAC command, or asynchronous data between the coordinator and the deviceor between the devices. In order to prevent data collision between thedevices in the unreserved CTB field, a carrier sense multiple access(CSMA) mode or a slotted Aloha mode can be used. If there are many kindsof control information or commands to be transmitted, the reservedregion can be set in the LRP channel. In each superframe, the length andthe number of reserved CTB fields and unreserved CTB fields can bevaried per superframe and are controlled by the coordinator.

Furthermore, although not shown in FIG. 6, each superframe includes acontention-based control period (CBCP) located next to the beacon totransmit urgent control/management messages. The length of the CBCP isset so as not to exceed a given threshold value mMAXCBCPLen.

FIG. 7 is a diagram illustrating a protocol layer structure implementedin a device of a WVAN.

Referring to FIG. 7, a communication module of each device included inthe WVAN can include four layers depending on its function. Generally,the communication module includes an adaptation sublayer 40, a MAC layer41, a PHY layer 42, and a station management entity (SME) layer 43. Inthis case, a station is a device for identifying the coordinator, andthe station management entity (SME) means a device management entity(DME). The station management entity (SME) is a layer independent entitythat controls a lower layer and collects status information of devicefrom each layer. The station management entity SME includes entitiesthat manage each layer of the communication module. In this case, anentity that manages the MAC layer will be referred to as a MAC layermanagement entity (MLME), and an entity that manages the adaptationlayer will be referred to as an adaptation layer management entity(ALME).

The adaptation sublayer 40 includes an AVC protocol 400 and an A/Vpacketizer 410. The AVC protocol 400 is an upper layer that performsdevice control and streaming connection for A/V data transmissionbetween a transmitting device and a receiving device. The A/V packetizer410 formats A/V data for HRP data service.

The MAC layer 41 takes the role in link setup, connection ornon-connection, and channel access to a lower layer of a materialtransmission protocol, and also takes the role in reliable datatransmission. In other words, the MAC layer 41 serves to transmit acontrol/data message or control a channel.

The PHY layer 42 directly processes A/V data, or the A/V data may beprocessed simultaneously by the PHY layer 42 and the MAC layer 31. ThePHY layer is responsible for the task to convert a message requestedfrom the upper layers such as the adaptation layer 30 and the MAC layer41, so that the message can be sent and received between devices by thePHY layer. Also, the PHY Layer includes the aforementioned two kinds ofphysical layers, HRP layer 420 and LRP layer 421.

The layers of the device provide services such as a high rate service, alow rate service, and a management service. The high rate service isused for video, audio and data transfer, and the low rate service isused for transmission of audio data, MAC command, and asynchronous dataof small capacity. The respective layers transmit and receive a simplemessage to and from each other before a process of data exchange isperformed between the respective layers. The message exchanged betweensuch different layers is referred to as primitive.

If the WVAN having the aforementioned feature starts, the coordinatorbelonging to the WVAN selects a specific channel, and two or moredevices belonging to the WVAN transmit and receive A/V data through acorresponding channel using a radio link. In order to select anoptimized physical layer for performing data transmission and receptionbetween the transmitting device and the receiving device, which belongto the WVAN, the transmitting device and the receiving device performlink assessment and link adaptation. The link may mean the channel ormay be similar to the channel. Link assessment is used as the samemeaning as channel assessment. For link adaptation, the transmittingdevice performs link recommendation after performing link assessment.

Meanwhile, the transmitting device is a device that transmits A/V datato another device through channel resources allocated from thecoordinator and may be used to refer to the transmitting device in viewof signal transmission and reception. The receiving device is a devicethat receives A/V data from the transmitting device and may be used torefer to the receiving device in view of signal transmission andreception.

A procedure of performing link adaptation between WVAN devices will bedescribed in brief with reference to FIG. 8.

FIG. 8 is a flow chart illustrating an example of a procedure forperforming link adaptation in a WVAN device according to one embodimentof the present invention.

Referring to FIG. 8, the WVAN transmitting device transmits a linkassessment request message to the receiving device that transmits andreceives A/V data (S10). The link assessment request message is torequest the device to perform assessment of the status of a channelcurrently in service. The receiving device assesses the status of thechannel currently in service in response to the link assessment requestmessage (S11). The channel assessment is performed in such a manner thatthe receiving device measures a packet error rate/ratio (PER), asignal-to-noise ratio (SNR), etc. while receiving at least one packet.The receiving device transmits link recommendation information to thetransmitting device, wherein the link recommendation informationincludes information acquired by channel assessment (S12). The linkrecommendation information may be transmitted if there is a linkrecommendation request from the transmitting device, or may betransmitted even without any link recommendation request.

The transmitting device which has received the link recommendationinformation determines a link adaptation method for performing linkadaptation (S13). Examples of the link adaptation method include anunequal error protection (UEP) method, a beam searching method, an HRPmode and/or LRP mode (hereinafter, referred to as ‘HRP/LRP mode’)adjustment method, and a transmission power control method. Thetransmitting device performs link adaptation using at least one of theabove methods in accordance with its status (S14).

Each of the steps will be described later in brief.

FIG. 9 is a flow chart illustrating an example of link assessment andlink recommendation in a WVAN device according to one embodiment of thepresent invention. Generally, link assessment can be used to assessquality of a channel used by the device.

Referring to FIG. 9, the transmitting device transmits a data packet tothe receiving device using a random channel (S20), and the receivingdevice performs a step (S21) of transmitting ACK packet for respondingto the transmitting device at least one time. At this time, thereceiving device can collect information of the status of the channelused in steps S20 and S21 or signal quality. If the channel assessmentrequest message is transmitted from the transmitting device (S22), thereceiving device performs channel assessment based on the information ofsignal quality or the channel status (S23). Since the wireless networkuses the HRP channel and the LRP channel, the receiving device performslink assessment for at least one of the HRP channel and the LRP channel.

Specifically, link assessment (or channel assessment) can be performedby measuring energy level, noise level, or interference level on thechannel for a time interval where data packets are received from thetransmitting device. However, parameters that can assess the channelstatus are not limited to the above parameters, and a frame error rate(FER), a bit error rate (BER), etc., which are measured during datareception can be used as the parameters that can assess the channelstatus.

The receiving device generates link recommendation information based onthe information of the measured channel status (or signal quality) andthen transmits the generated link recommendation information to thetransmitting device (S24). The link recommendation information caninclude information of the channel status measured by the receivingdevice.

During the link recommendation step (S24), as described above, thetransmitting device receives the link recommendation information thatincludes the information of the channel status used for signaltransmission and information of a PHY mode to be recommended.

The present invention relates to a link adaptation method of atransmitting device through transmission power control by includingtransmit power control(TPC) information in the link recommendationinformation. The link recommendation procedure will be described withreference to FIG. 12.

Next, the transmitting device can perform link adaptation to adjustparameters of the physical layer, thereby acquiring better quality ofservice (QoS) or higher throughput.

As described above, examples of the link adaptation method include anunequal error protection (UEP) method, a beam searching method, an HRPmode and/or LRP mode (hereinafter, referred to as ‘HRP/LRP mode’)adjustment method, and a transmission power control method. For linkadaptation, the WVAN transmitting device receives channel assessmentinformation and link recommendation information from the receivingdevice as described in FIG. 8 and uses at least one of the linkadaptation methods based on the channel assessment information and thelink recommendation information. The link recommendation informationincludes information required to use the link adaptation method.

Hereinafter, each of the link adaptation methods will be described inbrief.

According to the unequal error protection (UEP) method, when atransmission error occurs during uncompressed video data transmission,unequal protection is applied to bits having different importance levelsto perform fast recovery. Also, unequal protection is applied to bitshaving different importance levels through asymmetrical arrangement tobetter protect bits having high importance, thereby recovering thetransmission error. Specifically, the UEP can be performed by applyingasymmetrical coding or asymmetrical arrangement mapping for radiotransmission of uncompressed video data.

According to the beam searching method, the transmitting device and thereceiving device, which have at least one beamforming antenna group,select one or more antenna groups to be used for signal transmission andreception between devices before using beamforming. In a multi inputmulti output (MIMO) system that uses a plurality of antennas, the WVANdevice can use a directional signal for a specific target, i.e., beam,to maximize a signal-to-noise ratio. Beamforming is a type of a smartantenna and means that a directional signal is transmitted to a specifictarget using a plurality of antennas to enhance efficiency. Hereinafter,the beam searching method will be described in brief with reference toFIG. 10.

FIG. 10 is a flow chart illustrating an example of a procedure oftransmitting and receiving signals to perform a beam searching processbetween WVAN devices according to one embodiment of the presentinvention. Beam searching is not necessarily required to be performedduring initial communication but may be performed if necessary duringcommunication. Also, beam searching includes beam searching in HRPchannel and beamforming LRP channel.

Referring to FIG. 10, the WVAN transmitting device transmits a trainingsignal to the receiving device through each antenna group (S30). Thereceiving device performs channel estimation and signal detectionthrough the training signal (S30). The receiving device transmitsfeedback information obtained by the result of channel estimation andsignal detection to the transmitting device (S32). At this time, it ispreferable that training signals transmitted from a plurality ofbeamforming antenna groups of the transmitting device are sequentiallytransmitted as illustrated in FIG. 10. In other words, after the firsttraining signal is transmitted through the first beamforming antennagroup, the second training signal is transmitted through the secondbeamforming antenna group, and then the training signals are transmittedfrom the other beamforming antenna groups in due order. It is alsopreferable that the steps of transmitting feedback information from thereceiving device to the transmitting device are performed in due orderin accordance with the training signals transmitted from thetransmitting device.

As described above, the training signal and its feedback information maybe repeated for throughput detection of each of the plurality ofbeamforming antenna groups, and at the same time may be repeated severaltimes to measure rank of a channel matrix H (S33, S34, S35). After thesteps S33 to S35 are repeated, the transmitting device determines one ormore beamforming antenna groups to be used through the feedbackinformation (S36). The transmitting device can select an optimizedantenna group among the beamforming antenna groups having throughput ofa predetermined reference value or greater based on the detected result.Also, the feedback information transmitted from the receiving device mayinclude strength information of a signal received as a result of thesignal detection in step S21 or S24.

Accordingly, the transmitting device can select a beamforming antennagroup to be used and also determine an antenna array weight vector (AWV)to be applied to the selected beamforming antenna group. The AWV isdetermined based on received signal strength indication (RSSI)information between the transmitting device and the receiving device,which perform beamforming.

At this time, the training signal transmitted from the transmittingdevice is a signal obtained by a predetermined training sequence sharedbetween the transmitting device and the receiving device, and caninclude identification information of the transmitting device as thecase may be.

If a current antenna group is changed to another antenna group throughbeam searching, beam steering is performed. Beam steering means that adirection of a main loab of a beam pattern is changed by changing theantenna group used to transmit and receive a signal, wherein a radiosignal is transmitted and received in the main loab. Beam steering isperformed in such a manner that antenna location is changed in radiocommunication or phase of a radio signal is changed.

The beam searching method is an example of a method of adaptation to anew link, and the training signal and its feedback information in FIG.10 correspond to the link recommendation request message and the linkrecommendation information in FIG. 9.

Beam steering through beam searching can be applied if a communicationerror occurs due to obstacle existing between the WVAN transmittingdevice and the WVAN receiving device, which transmit and receive a radiosignal, or if a radio signal strays from an original pattern where theradio signal is transmitted.

The HRP/LRP mode adjustment means PHY mode adjustment of a channel usedby the WVAN transmitting device and the WVAN receiving device, whichcurrently transmit and receive a radio signal. PHY mode adjustment canbe used if a communication error occurs due to obstacle existing betweenthe devices, which transmit and receive a radio signal, or if aninterference rate increases due to increase of devices that use the samechannel. Accordingly, the transmitting device requests the receivingdevice of recommendation information of HRP mode and LRP mode duringlink recommendation to change the PHY mode of the current channel, andperforms link adaptation in such a manner that the PHY mode is changedto the HRP mode and the LRP mode recommended by the receiving device.

According to the transmission power control method, the WVAN device,which currently transmits a radio signal, controls the transmissionpower to reduce power consumption and maintain a reliable transmissionstatus. For example, if a physical distance between the devices becomeslong, RSSI may become weak. If the physical distance becomes short, RSSIincreases but power consumption may occur.

Accordingly, the transmitting device that transmits a signal canincrease or decrease the transmission power to correspond to a transmitpower control report (TPC) information element (TPC report IE) or a TPCrequest command transmitted from the receiving device. Alternatively,the receiving device can transmit a transmission power control requestmessage to the transmitting device in a type of MAC command. In thiscase, the receiving device should request the WVAN coordinator ofchannel resources to transmit the transmission power control requestcommand.

As described above, a proper one of the various link adaptation methodscan be used in accordance with the status of the WVAN device.Hereinafter, an example of a status of a WVAN device according to oneembodiment of the present invention during radio signal communicationwill be described in brief with reference to FIG. 11A to FIG. 11E.

FIG. 11A to FIG. 11E are diagrams illustrating an example that acommunication status is deteriorated by a status of a WVAN deviceaccording to one embodiment of the present invention.

FIG. 11A illustrates an example that an obstacle exists between WVANdevices that transmit and receive a radio signal. If an obstacle existsin a radio signal path between the devices, a communication error mayoccur due to signal reflection, etc. Accordingly, a change of a signaltransmission path is required. In this case, another signal transmissionpath having no obstacle is selected by beam searching and beam steeringis performed, or link adaptation can be performed using the HRP/LRP modeadjustment method currently in service.

FIG. 11B illustrates an example that a physical distance between a WVANtransmitting device and a WVAN receiving device, which transmit andreceive a radio signal, increases or decreases. If the physical distancebetween the devices increases, RSSI may become weak. If the physicaldistance between the devices decreases, RSSI increases but powerconsumption may occur. Accordingly, the transmitting device thattransmits a signal in accordance with the embodiment of the presentinvention can adjust the transmission power to be increased or decreasedin accordance with the RSSI caused by the physical distance between thedevices.

FIG. 11C illustrates an example that a location of any one of WVANdevices, which transmit and receive a radio signal, is changed. Eventhough the physical distance between the devices is maintained, if thelocation of the device is changed as illustrated in FIG. 11C, the signaltransmission path is changed to affect the channel status. Accordingly,the transmitting device requests the receiving device to perform beamsearching and performs beam steering by selecting another antenna groupbased on the feedback information transmitted from the receiving deviceand transmitting a signal.

FIG. 11D illustrates an example that a WVAN device, which transmits andreceives a radio signal, is affected by interference due to anotherdevice that uses the same channel as the current channel. Even thoughthe status of the current channel is good, if there are many otherdevices that use the same channel, an interference rate increases due toother devices. Accordingly, the WVAN device can perform HRP/LRP modeadjustment in the current channel.

FIG. 11E illustrates an example that one of WVAN devices that transmitand receive a radio signal is rotated. Even though there is no change inthe physical distance between the devices or location of the devices,since a location of a unidirectional antenna is continuously changed byrotation of the device, a communication status is deteriorated.Accordingly, the transmitting device requests the receiving device toperform beam searching and performs beam steering by selecting anotherantenna group based on the feedback information transmitted from thereceiving device and transmitting a signal.

In addition, the communication status may be deteriorated depending onvarious statuses of the device. In this case, a proper one of theaforementioned link adaptation methods may be selected as the case maybe. However, the link adaptation method is not limited to the selectedone. Also, two or more link adaptation methods may be used.

As described above, in order to perform link adaptation, thetransmitting device can receive link recommendation information, whichis required to perform the link adaptation method, from the receivingdevice during link recommendation.

Hereinafter, the link recommendation method will be described in brief.

The link recommendation method can be divided into an active mode and apassive mode, wherein the active mode is to transmit link recommendationinformation in response to a request of the transmitting device and thepassive mode is to transmit link recommendation information without anyrequest of the transmitting device.

FIG. 12 is a flow chart illustrating an example of a procedure ofperforming link recommendation between WVAN devices according to oneembodiment of the present invention. Specifically, FIG. 12 illustratesan example of link recommendation in the active mode.

Referring to FIG. 12, the receiving device receives a data packet fromthe transmitting device (S40). The receiving device transmits ACK packetin response to the data packet (S41) and generates an informationelement (IE) for link recommendation during reception. The informationelement (IE) for link recommendation is generated based on the result ofthe channel status measured in step S23 of FIG. 9. If a linkrecommendation request message is transmitted from the transmittingdevice (S42), the receiving device generates a response message to therequest message (S43). The link recommendation request message can beused to refer to the link assessment request message requesting linkassessment in FIG. 9. The receiving device can assess the channel statusafter receiving the link recommendation request message. The responsemessage includes the information element for link recommendation, whichis generated based on the channel status or signal quality collectedduring the step of receiving a data packet.

Afterwards, the receiving device a link recommendation response messageto the transmitting device (S44).

FIG. 13 is a flow chart illustrating another example of a procedure ofperforming link recommendation between WVAN devices according to oneembodiment of the present invention. Specifically, FIG. 13 illustratesan example of link recommendation in the passive mode.

Referring to FIG. 13, in the same manner as FIG. 12, the receivingdevice receives a data packet from the transmitting device (S40). Thereceiving device can measure the status of the channel currently inservice while repeating the step of transmitting ACK packet in responseto the data packet (S41). At this time, if it is determined that thestatus of the current channel is remarkably deteriorated or RSSI becomesweak (S45), the receiving device transmits a response message, whichincludes link recommendation information, in accordance with itsdiscretionary determination even though the transmitting device does nottransmit the link recommendation request message (S46).

The aforementioned link recommendation method of the active mode and thepassive mode can be divided into a normal link recommendation method anda fast link recommendation method in accordance with a data format fortransmitting the link recommendation request message and the linkrecommendation response message.

Examples of the link adaptation method based on the normal linkrecommendation method include a UEP method, a beam searching method, andan HRP/LRP mode adjustment method. According to the normal linkrecommendation method, the link recommendation request message and itsresponse message are transmitted in accordance with a type of MACcommand. The normal link recommendation method for performing linkrecommendation using the MAC command uses channel resources separatelyfrom data transmission to transmit the MAC command. Also, according tothe normal link recommendation method, the transmitting device transmitsa transmission power control request message to the receiving device asa separate MAC command and receives TPC information in response to thetransmission power control request message to control the transmissionpower. Alternatively, the receiving device can transmit MAC commandrequesting transmission power control in accordance with RSSI to thetransmitting device.

Accordingly, the transmission power cannot be controlled through thenormal link recommendation method.

On the other hand, the fast link recommendation method does not use theMAC command for link recommendation unlike the normal linkrecommendation method, and transmits a data packet or ACK packet, whichincludes the link recommendation request message and its responsemessage. Accordingly, the fast link recommendation method may not useseparate channel resources to perform link recommendation. Also, sincethe link recommendation process is performed during data transmissionand reception, the fast link recommendation method can be performedfaster than the normal link recommendation method.

The present invention relates to a link recommendation method thatincludes TPC information for link adaptation in the fast linkrecommendation method.

According to one embodiment of the present invention, examples of thelink adaptation method based on the fast link recommendation methodinclude a UEP method, beam searching method, an HRP/LRP mode adjustmentmethod, and a transmission power control method.

FIG. 14 is a flow chart illustrating another example of a procedure ofperforming link recommendation for transmission power control for linkadaptation between WVAN devices according to one embodiment of thepresent invention. Specifically, FIG. 14 illustrates an example of linkrecommendation in the active mode of the fast link recommendationmethod.

Referring to FIG. 14, the WVAN transmitting device transmits a datapacket to the WVAN receiving device, wherein the data packet includes anormal data packet and a composite data packet (S50). The normal datapacket is a data packet that includes a single sub-packet, and thecomposite data packet is a data packet that includes two to sevenmultiple sub-packets. If the WVAN transmitting device transmits thecomposite data packet, it transmits various messages or commands usingone data packet or two or more same sub-packets, thereby improvingreceiving accuracy as compared with the normal data packet.

The receiving device transmits ACK packet to the transmitting device inresponse to the data packet (S51). At this time, the receiving devicecan perform assessment of the communication status and the channelstatus during data reception, and can collect information for defining aproper transmission power value in accordance with received signalstrength (or receiving strength). The transmitting device can transmitthe data packet to the receiving device, wherein the data packetincludes link recommendation request information (S52). At this time,the link recommendation request information according to the embodimentof the present invention includes request information of transmissionpower control. The link recommendation request information may be usedto refer to the link assessment request message requesting linkassessment as described in FIG. 9, and the receiving device can assessthe channel status after receiving the link recommendation requestinformation.

The receiving device generates link recommendation information inaccordance with the result of channel assessment or received signalstrength information measured through the step S50 (S53). Also, thereceiving device may perform channel assessment after receiving the linkrecommendation request information.

The receiving device transmits link recommendation information to thetransmitting device in response to the link recommendation requestinformation, wherein the link recommendation information includes TPCinformation (S54). In this case, the link recommendation information isincluded in the ACK packet to the data packet that includes the linkrecommendation request information transmitted in step S52. Thetransmitting device decides whether to control the transmission power inaccordance with the TPC information included in the link recommendationinformation (S55). The transmitting device is not necessarily requiredto follow transmission power change details included in the TPCrecommendation information of the receiving device. If the transmittingdevice decides to change the transmission power, it is not required thatthe transmitting device should transmit a separate response message tothe receiving device. The transmitting device which has decided whetherto change the transmission power transmits data having the changedtransmission power or the original transmission power to the receivingdevice (S56).

In the fast link recommendation method, the transmitting device cantransmit link recommendation information without link recommendationrequest of the transmitting device.

FIG. 15 is a flow chart illustrating other example of a procedure ofperforming link recommendation for transmission power control for linkadaptation between WVAN devices according to one embodiment of thepresent invention. Specifically, FIG. 15 illustrates an example of linkrecommendation in the passive mode of the fast link recommendationmethod.

Referring to FIG. 15, the WVAN receiving device receives a data packetfrom the transmitting device, wherein the data packet includes a normaldata packet and a composite data packet (S50). And, the WVAN receivingdevice transmits ACK packet to the WVAN transmitting device in responseto the data packet (S51). At this time, the receiving device can performassessment of the communication status and the channel status duringdata reception, and can collect information for defining a propertransmission power value in accordance with received signal strength(RSSI) (S60).

In step S60, if the RSSI becomes weak remarkably, or if it is determinedthat power capacity greater than the required transmission power isrequired due to too great RSSI, the receiving device transmits linkrecommendation information to the transmitting device even without linkrecommendation request (S61). Likewise, the link recommendationinformation is included in ACK packet to the data packet received in theprevious step, and includes TPC information. The transmitting devicedecides whether to change the transmission power in accordance with theTPC information included in the link recommendation information (S62),and then transmits A/V data to the receiving device (S63).

In the fast link recommendation method, the link recommendation requestinformation is included in the data packet, which includes a MAC headerfield and a data field, wherein the MAC header includes the linkrecommendation request message.

The link recommendation information is included in the ACK packet to thedata packet transmitted from the transmitting device.

The ACK packet is divided into a directional low-rate physical data unit(LRPDU) ACK packet, an omni-directional LRPDU ACK packet, and abeam-formed LRPDU ACK packet. The directional LRPDU packet includes apacket having payload and a packet having no payload. The directionalLRPDU packet is mainly used during transmission of ACK signal orbeam-formed LRPDU packet. The directional LRPDU packet having payloadcan be used during transmission of beam searching feedback informationand beamforming feedback information. The omni-directional LRPDU packetcan be used during transmission of broadcasting signal or multiple LRPpackets. The beam-formed LRPDU packet can be used during transmission ofLRP packet at a high data rate.

The ACK packet that includes link recommendation information accordingto the embodiment of the present invention includes a directional LRPDUACK packet having a payload field and an omni-directional LRPDU ACKpacket. The link recommendation information can be included in anextension control field of the directional LRPDU ACK packet havingpayload or a MAC extension header of the omni-directional LRPDU ACKpacket. This can be determined depending on received data packet type.

However, it is only exemplary that the link recommendation requestinformation is included in the MAC extension header and the linkrecommendation information is included in the extension control field orthe MAC extension header.

Hereinafter, in order to describe an example of a packet type thatincludes the link recommendation request information and the linkrecommendation information, an example of the data packet oromni-directional LRPDU ACK packet will be described. The data packet oromni-directional LRPDU ACK packet commonly include a data format thatincludes a MAC header, an HCS field, and a packet body having aplurality of sub-packets as illustrated in Table 1.

TABLE 1 MAC header HCS Packet Body

The MAC header can be divided into an HRP MAC header and an LRP MACheader. Hereinafter, the MAC header will be described with reference toFIG. 16. The HCS field is located between the MAC header and the packetbody and includes CRCs of 32 bits. The packet body can include minimumsingle sub-packet to maximum seven sub-packets. The data packet can bedivided into a normal data packet and a composite data packet dependingon whether the packet body is a single sub-packet or multiplesub-packets. Each sub-packet can be set to have various sizes.

FIG. 16 is a diagram illustrating an example of a MAC header formattransmitted from a WVAN device according to one embodiment of thepresent invention, especially illustrates an example of a MAC headerthat includes a signal transmitted through HRP and LRP.

Referring to FIG. 16, the HRP MAC header format includes a MAC controlheader 90, a MAC extension header 91, a security header 92, a videoheader 93, a CP header 94, and a reserved field 95. The LRP MAC headerformat includes a MAC control header 90, a MAC extension header 91, asecurity header 92, a reliable broadcast or multicast (ReBoM) header 96,and a reserved field 95.

The MAC control header 90 includes a protocol of transmitted packet,packet control details such as packet type, identification informationidentifying a device that transmits a corresponding packet, andidentification information identifying a device that receives acorresponding packet.

The MAC extension header 91 includes information of a link having fasttransmission speed among links used for data transmission, informationof HRP and LRP modes, and one or more ACK groups. The ACK groupsrespectively correspond to sub-packets included in the packet bodyfield.

The security header 92 includes information identifying a key used forencryption or authentication of data transmitted through a packet.

The video header 93 included in the HRP MAC header only includesinformation of order and location of video data displayed in thereceiving device that receives the video data. The CP header 94 is usedto transfer contents protection information of packets, and its type canbe implemented in various manners depending on a contents protectionmethod used for corresponding data.

The ReBoM header 96 included in the LRP MAC header only includes forwardLRP packets if a bit within the ReBoM header is set to 1. Also, theReBoM header 96 includes an ACK response bitmap region indicatingwhether a device that transmits the forward LRP packets currently joinsa ReBoM process.

The link recommendation request information that includes TPCinformation according to the embodiment of the present invention and thelink recommendation information are included in the MAC extension header91 illustrated in FIG. 16.

FIG. 17 is a diagram illustrating an example of a MAC extension headerformat transmitted from a WVAN device according to one embodiment of thepresent invention.

Referring to FIG. 17, the MAC extension header includes an extensioncontrol field 100, a type field 101 including information of a data typeincluded in sub-packets constituting MAC packet, an LRP ADT feedbackinformation field 102, a reserved field 103, an ACK group informationfield 104, a pixel clock field 105 including clock information of videodata (for example, pixel), an audio clock field 106 including clockinformation of audio data, and 27 MHz clock field 107 including clockinformation of 27 MHz in a source device.

The type field 101 includes information indicating a type of dataincluded in sub-packets constituting a packet together with the MACheader. For example, if a bit value set in the field 101 is ‘0’, itindicates that the MAC command is transmitted through the sub-packets.If a bit value set in the field 101 is ‘1’, it indicates that data aretransmitted through the sub-packets. If a bit value set in the field 101is ‘2’, it indicates that audio signal is transmitted through thesub-packets. If a bit value set in the field 101 is ‘3’, it indicatesthat video signal is transmitted through the sub-packets. If a bit valueset in the field 101 is ‘4’, it indicates that a sequence for beamtracking is included in the sub-packets. If a bit value set in the field101 is ‘5˜F’, it indicates that use of the field is reserved.

The LRP ADT feedback field 102 includes antenna direction tracking (ADT)feedback information for obtaining an optimized transmission patternduring future signal transmission in an LRP unidirectional mode. The bitvalue set in the LRP ADT feedback field 102 represents index informationof an optimized transmitting device antenna, which is measured from anLRPDU of a finally received short-omni LRP preamble or an ADT postamblefield of a preceding unidirectional ACK packet.

The ACK group field 104, as illustrated in Table 2, includes one or morefields including information of sub-packets and a field includinginformation as to whether packet check sequence (PCS) is used. Table 2illustrates an example of a composite data packet.

TABLE 2 Bits: 1 1 . . . 1 1 Sub-packet 1 Sub-packet 2 . . . Sub-packet 1sb PCS

Since one packet includes a MAC header and a packet body that includesmaximum seven sub-packets, maximum seven fields can be provided asfields that include information of sub-packets constituting the ACKgroup 104.

The sub-packet information field constituting the ACK group 104 includesinformation indicating whether preceding sub-packets exist. For example,if 1 bit is allocated to each field as illustrated in Table 1 andpreceding sub-packets exist, the bit value of the sub-packet field isset to ‘1’. If no preceding sub-packets exist, the bit value of thesub-packet field is set to ‘0’. In this case, the bit value set in thefirst sub-packet field is always ‘0’.

The PCS field includes information indicating whether a packet checksequence (PCS) is used in the step of determining whether thesub-packets are received exactly. For example, in a state that 1 bit isallocated to the PCS field as illustrated in Table 1, if the PCS isused, the bit value is set to ‘1’. If not so, the bit value is set to‘0’.

Maximum five ACK groups can be defined. The receiving device thatreceives a data packet including the aforementioned ACK groupinformation transmits ACK/NACK signals to the transmitting device,wherein the ACK/NACK signals include information indicating whether eachACK group has received sub-packets.

The extension control field 100 includes link recommendation requestinformation and link recommendation information according to theembodiment of the present invention. The extension control field 100includes a fast link mode field 1000 indicating the presence of a fastlink mode, an HRP mode field 1001, an LRP mode field 1002, a transmitpower control(TPC) field 1003 including information for requestingrecommendation of transmission power control, and a reserved field 1004.

The fast link mode field 1000 includes information indicating whether acorresponding MAC extension header includes link recommendation requestinformation or link recommendation information in response to therequest information in the fast link recommendation scheme.

For example, in a state that 2 bits are allocated to the fast link modefield 1000, if the bit value is ‘00’, it indicates that linkrecommendation is not requested. If the bit value is ‘01’, it indicatesthat link recommendation is requested. If the bit value is ‘10’, itindicates that link recommendation information is included in the fastlink mode field. If the bit value is ‘11’, it indicates that use of thefield is reserved. Accordingly, in the aforementioned embodiment, if thetransmitting device requests the receiving device of linkrecommendation, the bit value of ‘01’ is set to the fast link mode field1000. If the receiving device transmits the link recommendationinformation to the transmitting device, the bit value of ‘10’ is set tothe fast link mode field 1000. However, message types indicated by thebit values corresponding to the fast link mode field 1000 are onlyexemplary, and modifications can be made in the message types indicatedby the bit values. Various kinds of link recommendation mode informationcan be transferred depending on the bits allocated to the fast link modefield.

The HRP mode field 1001 and the LRP mode field 1002 may be used as anHRP request field and an LRP request field depending on the bit valuesset in the fast link mode field 1000, or may include responseinformation to the request. Namely, if the fast link mode field 1000includes link recommendation information, the HRP mode field 1001 andthe LRP mode field 1002 includes information of HRP mode and LRP mode tobe recommended by the receiving device.

The HRP mode field 1001 includes information indicating whether tochange the HRP mode currently in service and index information of theHRP mode to be recommended if the current HRP mode is changed. Forexample, as 4 bits are allocated to the HRP mode field, if the bit valueof the HRP mode field is set to ‘1111’, it is recommended that thecurrent HRP mode is maintained. At this time, if the transmitting deviceis using a spatial multiplexing (SM)-HRP mode, the receiving device canselect the HRP mode based on data streams having the highest signalstrength.

Likewise, the LRP mode field 1002 includes information indicatingwhether to change the LRP mode currently in service and indexinformation of the LRP mode to be recommended. For example, as 3 bitsare allocated to the LRP mode field 1002, if the bit value of the LRPmode field is set to ‘111’, it is recommended that the current LRP modeis maintained.

In this case, the HRP mode includes one or more modes depending on acode mode applied to data included in each of sub-packets constituting apacket body, a modulation scheme, a coding rate, etc. The coding modecan be divided into a coding mode of the aforementioned unequal dataprotection, a coding mode of an equal error protection (EEP), and a mostsignificant bit (MSB) retransmission scheme. The modulation schemeincludes quadrature phase-shift keying (QPSK) scheme and 16-quadratureamplitude modulation (QAM) scheme. The QPSK scheme is a modulationscheme that 2 bits are transmitted to correspond to four phases ofcarriers. The 16-QAM scheme is a modulation scheme that amplitude andphase of carriers are combined with each other to represent one signalusing 4 bits of 16 levels.

Examples of the LRP include omni-directional LRP, directional LRP, andbeamforming LRP. The LRP mode includes one or more modes depending on amodulation scheme, a forward error correction (FEC) mode, a PHY datarate mode, and a repetition period. In the LRP, a binary phase-shiftkeying (BPSK) scheme is used as the modulation scheme. The FEC mode isused such that a recipient predicts a message using repeated bits. TheFEC mode includes one or more modes depending on the repeated bits.

The TPC field 1003 includes TPC information. Likewise, the TPC field1003 is identified as a field for requesting TPC information or a fieldfor transmitting TPC information depending on the bit value set in thefast link mode field 1000. If the fast link mode field 1000 includesindication information indicating that the fast link mode field 1000includes link recommendation information, the TPC field 1003 can includeTPC information.

For example, as 2 bits are allocated to the TPC field 1003, if the bitvalue is set to ‘00’, it is recommended that the current transmissionpower should be maintained. If the bit value is set to ‘01’, it isrecommended that the transmission power should increase by 2 dB. If thebit value is set to ‘10’, it is recommended that the transmission powershould decrease by 2 dB. If the bit value is set to ‘11’, it indicatesthat use of the TPC field is reserved. However, information indicated bythe bit values set in the TPC field 1003 is only example of TPCrecommendation information, and can be varied. Also, if bits allocatedto the TPC field 1003 increase, more various power offsets than 2 dBindicated in the aforementioned can be recommended, and the informationindicated by the bit values set in the TPC field 1003 can also includeinformation of transmission power change cause.

Meanwhile, the transmitting device according to the embodiment of thepresent invention may request the receiving device of detailed TPCinformation before deciding whether to change the transmission powerbased on the TPC information received during link recommendation.

FIG. 18 is a diagram illustrating other example of a link recommendationprocedure for transmission power control for link adaptation in a WVANdevice according to one embodiment of the present invention.Specifically, FIG. 18 illustrates an example of link recommendation inthe active mode of the fast link recommendation method.

Referring to FIG. 18, the WVAN receiving device receives a data packetfrom the WVAN transmitting device, wherein the data packet includes anormal data packet and a composite data packet (S50). Then, the WVANreceiving device transmits ACK packet in response to the data packet andtransmits link recommendation information in accordance with a requestof the transmitting device, wherein the link recommendation informationincludes TPC information (S51 to S54). These steps S50 to S54 are thesame as those illustrated in FIG. 14. For briefness of description,description of the same steps will be omitted.

The transmitting device which has received link recommendationinformation including TPC information from the receiving device inaccordance with the embodiment of the present invention can transmit aprobe request message for requesting a TPC information element (S70).The receiving device transmits a probe response message to thetransmitting device in accordance with the probe request message,wherein the probe response message includes TPC information and RSSIinformation (S71).

In other words, according to the embodiment of the present inventionillustrated in FIG. 18, the transmitting device may request thereceiving device of required information before performing control oftransmission power, and decide whether to control the transmission powerbased on the requested information (S72). The transmitting device cantransmit data to the receiving device by using the transmission powerchanged during next data transmission or in a state that the originaltransmission power is maintained (S73).

Also, even in the fast link recommendation method of the passive mode,the transmitting device according to the embodiment of the presentinvention can request the receiving device of TPC information elementbefore deciding whether to change the transmission power.

FIG. 19 is a diagram illustrating an example of a data format thatincludes a probe request message transmitted from a WVAN transmittingdevice according to one embodiment of the present invention. The proberequest message is transmitted from the transmitting device to thereceiving device as a command requesting an information element (IE) tobe requested by the transmitting device, i.e., but not limited to, a MACcommand type.

Referring to FIG. 19, the probe request message transmitted from thetransmitting device to the receiving device includes a command ID field110 including identification information indicating a MAC command type,a MAC command length field 111, and an information element (IE) indexfield 112 including at least one IE index to be requested.

The IE index field 112 means index of IE to be requested by the devicethat transmits the probe request message, and can indicate aninformation element (IE) of a new coordinator, an information element(IE) of a power save mode, and an information element (IE) of WVANparameter change. According to one embodiment of the present invention,the transmitting device can set index of an information element relatedto control of transmission power in the IE index field 112.

The probe request message can be transmitted to one or more devices orcoordinators, and the device or coordinator which has received the proberequest message can transmit the probe response message. However, thedevice or coordinator is not necessarily required to transmit theresponse message. The receiving device which has received the proberequest message requesting a TPC IE can transmit a TPC report IE as theprobe response message in accordance with the embodiment of the presentinvention.

FIG. 20 is a diagram illustrating an example of a data format thatincludes a probe response message transmitted from a WVAN deviceaccording to one embodiment of the present invention. Specifically, thedata format includes a TPC report IE. The probe response message can betransmitted in, but not limited to, a MAC command type.

Referring to FIG. 20, the probe response message includes a command IDfield 120 including ID indicating a command type, a length field 121indicating a MAC command length, and an IE field 122 including at leastone requested IE.

The IE field 122 is to indicate an information element (IE) included inthe probe request message. If the IE field 122 includes a TPC IE inaccordance with the embodiment of the present invention, as illustratedin FIG. 20, the IE field 122 includes an IE index field 1220, a lengthfield 1221 indicating a length of an IE, a transmission power field 1222indicating transmission power used during signal transmission, and anRSSI field 1223 indicating RSSI.

The transmission power field 1222 can indicate a power level using 2'scomplement notation in a unit of dB. For example, a power level of +2 dBis set to 0×02 bits, and a power level of −2 dB is set to 0×FE bits.

The RSSI field 1223 indicates strength of a currently received signal,which is measured relatively to sensitivity of the receiving device. Forexample, if the RSSI is measured as 6 dB through sensitivity of thereceiving device in the current physical layer mode, the RSSI field 1223can be set to 0×06 bits.

The transmitting device which has received the probe response messageincluding the TPC IE can control the transmission power based on the TPCIE.

FIG. 21 is a diagram illustrating an example of a broadcasting signalprocessing system that includes a WVAN device according to oneembodiment of the present invention.

Generally, the WVAN device can play A/V data through processes whichwill be described layer, wherein the A/V data are input from at leastone of a broadcasting station, cable, satellite, and other WVAN devicethrough an antenna. If the WVAN device receives data from other device,it could be a receiving device. If the WVAN device transmits data toother device, it could be a transmitting device. Also, the WVAN devicecan perform message exchange with the coordinator.

Referring to FIG. 21, the broadcasting signal processing systemaccording to the embodiment of the present invention includes areceiving device 150, a remote controller 160, a local memory device170, and a network device 180 for performing wireless communication witha transmitting device 190.

The receiving device 150 that receives A/V data includes a receivingmodule 151, a demodulation module 152, a decoding module 153, a displaymodule 154, a control module 155, a graphic processor 157, atransmitting module 158, and a control signal communication module 159.In the example of FIG. 21, the transmitting device further includes alocal memory device 170 directly connected with the transmitting module158 that includes input and output ports. However, the local memorydevice 170 may be a memory device mounted in the transmitting device150.

The transmitting module 158 can communicate with a wire/wireless networkdevice 180, and can be connected with at least another device 190through the network device 180, wherein the at least one device 190exists on the wireless network. The control signal communication module159 receives a user control signal in accordance with a user controldevice, for example, remote controller, and outputs the received signalto the control module 155.

The receiving module 151 could be a tuner that receives a broadcastingsignal of a specific frequency through at least one of ground wave,satellite, cable, and Internet network. The receiving module 151 may beprovided respectively for each of broadcasting sources, for example,ground wave broadcasting, cable broadcasting, satellite broadcasting,and personal broadcasting. Alternatively, the receiving module 151 maybe a unified tuner. Also, supposing that the receiving module 151 is atuner for ground wave broadcasting, at least one digital tuner and atleast one analog tuner may be provided respectively, or a digital/analogtuner may be provided.

Furthermore, the receiving module 151 may receive internet protocol (IP)streams transferred through wire and wireless communication. If thereceiving module 151 receives IP streams, the receiving module 151 canprocess transmitting and receiving packets in accordance with an IPprotocol that establishes source and destination information forreceived IP packets and packets transmitted from the receiver. Thereceiving module 151 can output video/audio/data streams included in thereceived IP packets in accordance with the IP protocol, and can generatetransport streams to be transmitted to the network as IP packets inaccordance with the IP protocol so as to output them. The receivingmodule 151 is an element that receives an externally input video signal,and, for example, may receive IEEE 1394 type video/audio signals or HDMItype streams from the outside.

Also, the receiving module 151 can receive link recommendation requestinformation from the transmitting device in accordance with oneembodiment of the present invention, wherein the link recommendationrequest information includes TPC request information.

The demodulation module 152 demodulates broadcasting signals among datainput through the receiving module 151 or broadcasting signalstransmitted from the receiving device in an inverse order of amodulation mode. The demodulation module 152 outputs broadcastingstreams by demodulating the broadcasting signals. If the receivingmodule 151 receives stream type signals, for example, IP streams, the IPstreams are output to the decoding module 153 after bypassing thedemodulation module 152.

The decoding module 153 includes an audio decoder and a video decoder,and decodes the broadcasting streams output from the demodulation module152 through a decoding algorithm and outputs the decoded streams to thedisplay module 154. At this time, a demultiplexer (not shown) thatsplits each stream in accordance with a corresponding identifier mayadditionally be provided between the demodulation module 152 and thedecoding module 153. The demultiplxer splits the broadcasting signalsinto an audio element stream (ES) and a video element stream and outputsthem to each decoder of the decoding module 153. Also, if a plurality ofprograms are multiplexed in one channel, the demultiplexer selects onlya broadcasting signal of a program selected by a user and splits theselected broadcasting signal into a video element stream and an audioelement stream. If data streams or system information streams areincluded in the demodulated broadcasting signals, they are split by thedemultiplexer and then transferred to a corresponding decoding block(not shown).

The display module 154 displays broadcasting contents received from thereceiving module 151 and contents stored in the local memory device 170.The display module 154 can display a menu indicating whether the memorydevice has been mounted in the transmitting device and informationrelated to the remaining capacity of the memory device, in accordancewith a control command of the control module 155, and can be operatedunder the control of the user.

The control module 155 can control the operations of the aforementionedmodules (receiving module, demodulation module, decoding module, displaymodule, graphic processor, spatial multiplexing precoder and beamformingmodule, and interface module). Also, the control module 155 displays amenu that receives a control command of the user, and drives anapplication that displays various kinds of information or menu of thebroadcasting signal processing system for the user.

For example, the control module 155 can read out the contents stored inthe local memory device 170 if the local memory device 170 is mounted inthe transmitting device. Also, the control module 155 can control theoperation of the local memory device 170 so that the broadcastingcontents received from the receiving module 151 are stored in the localmemory device 170 if the local memory device 170 is mounted in thetransmitting device. Furthermore, the control module 155 can output acontrol signal for mounting the local memory device 170 depending onwhether the local memory device 170 has been mounted in the transmittingdevice.

The control module 155 checks remaining memory capacity of the localmemory device 170, and allows information of the remaining memorycapacity to be displayed for the user on the display module 154 throughthe graphic processor 157. The control module 155 can shift the contentsstored in the local memory device 170 to the remote memory device if theremaining memory capacity of the local memory device 170 is notsufficient. In this case, the control module 155 can display a menuindicating whether to shift the contents stored in the local memorydevice 170 to another local memory device (not shown) or the remotememory device through the display module 154. And, the control module155 can receive and process a user control signal of the menu.Accordingly, the control module 155 can allow the contents stored in thelocal memory device 170 and other directly or remotely mounted memorydevice to be shifted between them and stored therein.

Also, the control module 155 can assess the channel status or measureRSSI during signal reception through the receiving module 151. Accordingto the aforementioned embodiment, the control module 155 can measuretransmission power capacity for proper RSSI if the measured RSSI ischanged due to change of the physical distance between the transmittingdevice and the receiving device. And, the control module 155 cangenerate link recommendation information including TPC information andcontrol the transmitting module 158 to transmit the generated linkrecommendation information to the transmitting device. At this time, thegenerated link recommendation information is transmitted to thetransmitting device by being encapsulated in the ACK/NACK signal to thedata transmitted from the transmitting device.

The graphic processor 157 processes a graphic to be displayed so that amenu screen is displayed in a video image displayed by the displaymodule 154, and controls the graphic to be displayed in the displaymodule 154 together with the menu screen.

The transmitting module 158 can be used to transmit the data packetgenerated by the control module 155 to other device 190 through the wireand wireless network, or transmit data from the transmitting device 150to another device.

Also, the transmitting module 158 can include an interface module toperform bidirectional communication between the devices belonging to theWVAN. The interface module can be interfaced with at least one otherdevice 190 through the wire and wireless network. Examples of theinterface module include Ethernet module, Bluetooth module, shortdistance wireless Internet module, portable Internet module, home PNAmodule, IEEE1394 module, PLC module, home RF module, and IrDA module.

If the broadcasting signal processing system illustrated in FIG. 21includes the transmitting device according to one embodiment of thepresent invention, elements or modules constituting the device and thesystem include the same as those illustrated in FIG. 21. However, thetransmitting device can receive link recommendation informationincluding TPC information from the receiving device through thereceiving module 151, and the control module 155 can perform linkadaptation in accordance with the link recommendation information. Also,the control module 155 can generate link recommendation requestinformation requesting the receiving device of link recommendationinformation and control the transmitting module 159 to transmit thegenerated link recommendation request information to the receivingdevice. At this time, the generated link recommendation requestinformation is transmitted to the receiving device by being encapsulatedin the data packet transmitted to the receiving device. Also, thecontrol module 155 may decide whether to control the transmission powerin accordance with the TPC information included in the linkrecommendation information.

The terms herein can be replaced with other terms. For example, “device”can be replaced with user device (or machine), station, etc., and“coordinator” can be replaced with coordinating (control) device,coordinating (or control) station, piconet coordinator (PNC), etc. Also,the WVAN parameter configuring the WVAN can be used to refer to networkconfiguration information.

It will be apparent that some claims referring to specific claims may becombined with another claims referring to the other claims other thanthe specific claims to constitute the embodiment or add new claims bymeans of amendment after the application is filed.

Also, the data packet means information which is transmitted andreceived, such as message, traffic, video/audio data packet, controldata packet, but not limited to a specific data packet. Also, themessage can be used to refer to command.

Finally, examples of devices that can perform communication in acommunication system include computers, PDAs, notebook computers,digital TVs, camcorders, digital cameras, printers, mikes, speakers,headsets, bar-code readers, displays, and cellular phones. All digitaldevices can be used as the devices.

It will be apparent to those skilled in the art that the presentinvention can be embodied in other specific forms without departing fromthe spirit and essential characteristics of the invention. Thus, theabove embodiments are to be considered in all respects as illustrativeand not restrictive. The scope of the invention should be determined byreasonable interpretation of the appended claims and all change whichcomes within the equivalent scope of the invention are included in thescope of the invention.

1-20. (canceled)
 21. A method of exchanging messages at a transmittingdevice in a wireless network, the method comprising: transmitting afirst data packet to a receiving device; and receiving linkrecommendation information from the receiving device, wherein the linkrecommendation information comprises transmit power control (TPC)information for controlling transmission power to be used fortransmission.
 22. The method of claim 21, further comprisingtransmitting link recommendation request information to the receivingdevice, wherein the link recommendation request information is forrequesting link recommendation.
 23. The method of claim 22, wherein thelink recommendation request information is included in a Medium AccessControl (MAC) extension header of a second data packet transmitted tothe receiving device.
 24. The method of claim 23, wherein the linkrecommendation information is included in an Acknowledgment (ACK) packetreceived in response to the second data packet.
 25. The method of claim24, wherein the link recommendation information is included in a MACextension header of the ACK packet.
 26. The method of claim 25, whereinthe MAC extension header comprises a extension control field comprisingcontrol information, a type field indicating a type of data included insub-packets constituting a MAC packet, a low-rate physical (LRP) antennadirection tracking (ADT) feedback field comprising ADT feedbackinformation for obtaining an optimized transmission pattern during afuture signal transmission in an LRP unidirectional mode, an ACK groupfield comprising information indicating whether preceding sub-packetsexist and at least one of a clock field comprising clock countinformation of video data or audio data.
 27. The method of claim 26,wherein the extension control field comprises a link mode fieldindicating a type of link recommendation, a high-rate physical (HRP)mode field indicating a recommended HRP mode to be used at thetransmitting device, a LRP mode field indicating a recommended LRP modeto be used at the transmitting device and a TPC field comprising the TPCinformation.
 28. The method of claim 27, wherein the link mode fieldindicates any one of “link recommendation is not being requested”, “linkrecommendation request” and “link recommendation response”.
 29. Themethod of claim 21, wherein the link recommendation information isreceived without a request for link recommendation of the receivingdevice.
 30. The method of claim 29, wherein the link recommendationinformation is included in an Acknowledgment (ACK) packet received inresponse to a second data packet transmitted to the receiving device.31. The method of claim 30, wherein the link recommendation informationis included in a Medium Access Control (MAC) extension header of the ACKpacket.
 32. The method of claim 31, wherein the MAC extension headercomprises a extension control field comprising control information, atype field indicating a type of data included in sub-packetsconstituting a MAC packet, a low-rate physical (LRP) antenna directiontracking (ADT) feedback field comprising ADT feedback information forobtaining an optimized transmission pattern during future signaltransmission in an LRP unidirectional mode, an ACK group fieldcomprising information indicating whether preceding sub-packets existand at least one of a clock field comprising clock count information ofvideo data or audio data.
 33. The method of claim 32, wherein theextension control field comprises a link mode field indicating a type oflink recommendation, a high-rate physical (HRP) mode field indicating arecommended HRP mode to be used at the transmitting device, a LRP modefield indicating a recommended LRP mode to be used at the transmittingdevice and a TPC field comprising the TPC information.
 34. The method ofclaim 33, wherein the link mode field indicates any one of “linkrecommendation is not being requested”, “link recommendation request”and “link recommendation response”.
 35. The method of claim 21, whereinthe link recommendation information is determined based on a channelstatus for a channel on which the first data packet is transmitted. 36.The method of claim 21, wherein the TPC information comprises a valueindicating a recommendation for controlling transmission power in thetransmitting device.
 37. The method of claim 36, wherein the valueindicates that no change of a transmission power is recommended.
 38. Themethod of claim 36, wherein the value indicates that increase of atransmission power is recommended by a predetermined amount.
 39. Themethod of claim 36, wherein the value indicates that decrease of atransmission power is recommended by a predetermined amount.
 40. Atransmitting device of a wireless network, the transmitting devicecomprising: a receiving module; a transmitting module transmitting afirst data packet to a receiving device; and a control module receivinglink recommendation information including transmit power control (TPC)information for controlling transmission power to be used fortransmission from the receiving device through the receiving module, andcontrolling the transmission power in accordance with the TPCinformation.